Download Reviewer: Amanda Holland   Carolyn Pucko manuscript “Using Long­term Ecological Data to Identify Altitudinal Shifts of 

Reviewer: Amanda Holland Carolyn Pucko manuscript “Using Long­term Ecological Data to Identify Altitudinal Shifts of Species and Communities in Response to Recent Climate Change” Summary: This paper examines whether changes in vegetation composition over an elevation gradient are shifting as species communities or as individuals. They identified that the species of this montane environment are shifting as individuals and the species distribution changes can be explained by climate and anthropogenic changes (acid deposition) that are creating different temperature fluctuations, soil chemistry, and light availability. Evaluation: The abstract starts off the paper with a good briefing on the study itself and lays out the data to be examined. I would recommend restating the acid deposition tie; currently it is first mentioned in the abstract main conclusions and up until this point the broader topic was on discussing climate interactions. I would suggest a tie in earlier would be helpful even if it was not something that was considered for an initial driver of the system or to focus the first sentence of the conclusions on the climate interactions and then following with a statement on the non‐climate environmental changes. The material presented in the introduction sets‐up the different aspects under consideration for the research starting with the two differing hypothesis in this field, describing the species community behavior to environmental conditions. From the introduction material, I did not get a good grip on what was meant by ‘novel climate’ in the third paragraph of the introduction, was this to convey that climate patterns have a complex nature? Perhaps it would help clarify this by describing what the components of climate are as mentioned on line 83 of text. The aims paragraph and following paragraphs on the montane environment and historic climate in region provide good justification for why this study will be able to add clarity to this subject. I would suggest removing the final paragraph of the introduction on the statistical methods, as it seems more appropriately placed in the methods section where you already give justification for the use of these statistics. As mentioned above, the methods section gives a thorough discussion of the data used and methods taken for analysis. To further describe the chronosequence used for data analysis, I would include the years of analysis (1965, 1979, 1983, 1986, 2006) in this section. The first indication that multiple years were used in the analysis, other than the overall time period of 1965‐2006, was on line 250 when stated “3 of the 5 years”. The results and discussion section is very smooth with the figure presentation and accompanying observations. The result of the 2006 species communities being more similar to the higher elevation of 1965 species was a pattern that was easily interpreted by use of the multipart figure and the text. The same can be said for figure 3 and its results. In the discussion of Figure 1 it would be a good to have a statistic that would accompany the interpretation of the low and high elevation climate records to say there is a significantly greater change in temperature at the lower elevations. Through visual interpretation the lower elevation seems to have a steeper slope but the variability around the lines seem similar for both elevations. For figures 4‐6, I easily followed the results and discussion based on the optimal elevation or shift line but I had a harder time understanding this relationship visually with the points displayed on these graphs. An added sentence in the figure captions that clarifies how to interpret these would be helpful. In relation to Table 1, I could see the pattern that understory are moving at a different rate than the overstory by looking at the final time period for both variables. This relates back to what was described in the study site section, the overstory species are made up of certain communities and likely will change at a rate slower than the understory. However, the variability in the understory shifts in the table are not mentioned. The understory shift between 1965‐1986 is almost 20m higher than the compared time periods before and after, is there an explanation for what was occurring at this time? I think it would have better presentation at the end of the discussion to give a statement on the variability of the data in Table 1 if you are going to be presenting all the intermediate time periods. Status of paper & recommendations: I recommend this paper be accepted by the journal ‘Diversity and Distributions’ as it describes the multiplicative nature of individual and community distribution and relevant site interactions (in this case both climate and anthropogenic) that were influencing factors. • Would recommend a reorganization of the introduction paragraphs to start with the paragraph on the accepted hypotheses, followed by the climate and model paragraphs. This would shift the aims to come after this more introductory material followed by a paragraph that combines the montane environment and historic climate material. I think some of material in these last two paragraphs could be moved to the site description section as it is directly following and the information is site/region specific. o I think these changes would create a stronger focus in the beginning describing what the current literature says and then how your research compliments and adds to the field by ending with the study aims and justification of why the study site will provide clarification of these concepts. Edits for compliance with Journal: This paper conforms to the majority of the intended journal’s format. I would check before submission of paper that the figures match the desired format with labeling multi part figures with a, b, c, etc and color specifications. Would also look into the preference for order of citations listed in text, should citations in the text be listed alphabetical or chronological as I think this order is interchanged in the manuscript (example lines 59‐61 of introduction). Joe Bartlett 2/3/09 Pucko and Beckage critical review This study examined whether the montane understory plant communities present on Camel’s Hump were responding to climate warming with a individualistic or a community shift. Historic data shows that temperatures have increased over the past 40 years and as a result, overstory and understory vegetation are moving upslope. This study found greater shifts at higher elevations where temperature increases were present, but less pronounced than at lower elevation. A varied response between different individual species was identified through the use of Bayesian modeling. They also determined that understory vegetation is moving upslope faster than overstory vegetation. These findings have important implications for predicting the composition of forests in a warming environment This paper is well written and is successful in describing the study and conveying the results and conclusions. This is important since relatively complex statistical analyses and modeling methods were used. This paper is not quite at the final draft stage and as such there are some minor tense, grammar, sentence structure, and wording issues. There are also a few sentences with language better suited for a proposal than a report; we will do this…etc. The abstract is good considering the strange format required for submission. The introduction contains a very thorough literature review and provides a good background for the study. The purpose statement is a bit awkward and should possibly be moved to the end of the introduction instead of breaking up the literature review section. The paragraph on the historical dataset is also somewhat out of place and might be better incorporated into the study site section. The field methods section does a decent job describing a rather complex sampling design; a rough drawing of the sampling design may be very helpful. The NMDS and Bayesian modeling methods are well written and fairly clear given my lack of experience with these methods. The results and discussion section may benefit from an opening paragraph that gives an overview of the results before diving into major conclusions. Also, an appendix of summarized field data would be a good addition. The discussion on high elevation red spruce die‐off may warrant a mention on how this may affect the NMDS analysis. The conclusion section is very good. Specific recommendations for changes are as follows: L57 Consider splitting this into a paragraph for each hypothesis L57 Consider adding a real world example of the 2 types of shifts from the literature. L71 Too many “if” statements, try stating your hypothesis with stronger language L71 Purpose statement is a bit awkward: The goal of this study is to test the differing hypotheses of species or community shifts in response to climate warming by examining the understory community… L110 this paragraph needs to go with the study site section Throughout, much of the language is written as if a proposal – we will do this L141 Mention the avg temp/precip for mt Mansfield instead of just BTV Throughout watch tense L174 sampling design is confusing, consider adding a drawing of the sampling plot layout L201 Do you need to comment on potential effects of historic destructive sampling? L262 Start the R&D section with some results before going straight to major conclusions L274 awkward but important paragraph, consider rewording L280 can you infer “significance” from NMDS? L285 Move the acid rain sentence up to here to make the paragraph flow better L310 How much does this documented red spruce decline affect your NMDS? Could you consider dropping it from the analysis? Would like to see more discussion on the problems encountered with such a long term dataset – more info on destructive sampling etc. L657 Excellent figure captions This article meets all of the guidelines for a biodiversity research and reviews article and should be accepted with moderate revisions to the Diversity and Distributions Journal. Lee Corbett
GEOL 371
2/4/09
Review of: Using Long-term Ecological Data to Identify Altitudinal Shifts of Species and
Communities in Response to Recent Climate Change
Authors: C. Pucko and B. Beckage
In this manuscript, the authors present the findings of a long-term vegetation study on Camels
Hump in Vermont. The study focuses on understory vegetation plots along an altitudinal transect
that were first created in 1965. The authors attempt to quantify the amount of vegetation shift
(both in terms of communities and individual species) that has occurred over the past 40 years as
a result of warming temperatures.
Overall, the manuscript is well written, clear, and organized in a logical fashion. Although the
research is far out of my field, I had an easy time understanding most of the material because the
authors’ writing was very accessible. It seems as though this research is filling a much-needed
void in the current literature and will help to clarify how understory vegetation communities
change and migrate as a result of evolving climate. These results will be important in modeling
and predicting future impacts of climate change.
Please refer to the hand copy edited version of the manuscript for small comments regarding
structure and rhetoric. In addition, I have several broader comments for the authors:
1.) Your introduction is well-written and strong. Unfortunately, the last paragraph is more
methods-related and you lose some of that momentum you worked so hard to build up. Is it
possible to move some/all of this material to the methods section? Ending the introduction with
your second to last paragraph would be more powerful.
2.) In your methods section, you do a good job describing the field methods used to collect
species data. This might be an ignorant question, due to the fact that I know nothing about living
things, but I was wondering whether you should address the accuracy of your data. Were the
people doing the plant identification experts in the field? How easy is it to misidentify a species?
Were there any quality checks or quality control measures taken? Was all of the identification
conducted in a similar fashion?
3.) I liked the statistical modeling you conducted to study community shift and I think you
described it well. However, I was a little put off by the last sentence in the community shift
section. Couldn’t there be numerous environmental variables that would contribute to a unified
direction of community shift? I think your paper would be greatly strengthened if you could
make a better linkage between the shift you observed and climate. Is there any additional data
you could use to rule out other possibilities or to demonstrate that climate is the most likely
cause? Or are there any other manuscripts you could cite that have similar findings? If not, it
might not be appropriate to have “Climate Change” in your title if you’re not reasonably certain
that it is the key controlling factor for community and species migration.
4.) I was a little bit confused about how you attempted to differentiate between community shift
and species shift. You mention using a model that finds the ideal elevation for each species and
then comparing this ideal with the data you gathered throughout the study. How was the ideal
elevation for each species determined? How do you know the accuracy of this method? The
analysis you do here, and your conclusion that species are moving independently, is quite clever.
It would be helpful to strengthen it with more information regarding how the ideal elevations
were determined.
Good luck with edits and publication. Well done!
Lee Corbett
[email protected]
Using Long-term Ecological Data to Identify Altitudinal Shifts of Species and
Communities in Response to Recent Climate Change
Review by Christina Syrrakou
02/04/09
The manuscript presented studies the movement of species in a single understory
community due to changes in their environment and aims at determining whether those
species respond individualistically or similarly, as intact units. The area under study is
located in Camels Hump in the Green Mountains of Vermont, USA. For the process of
the data the writers used statistical methods and modeling and finally concluded that for
the specific case, species seem to respond as individuals.
Generally, the text presented is very well written and in formal language, which
gives a serious tone and shows that the writers have devoted a lot of time for both the text
as well as the research part of this paper. Also, the manuscript contains a significant
amount of technical terms, which indicates that it mostly addresses people with a
background in ecology and not so much a broader audience. The paper contains a big
amount of info and data and the results are carefully explained and in a logical way try to
show to the reader the analysis of the thoughts of the writer. However, I have to admit,
that taking into consideration my lack of background on this matter, it was a difficult and
at some points tiring text to follow but as I mentioned earlier it seems a serious work and
I believe that after some revisions it should be published.
•
First of all, the first two paragraphs of the introduction are well written helping
the reader get a general idea on the subject and the aim of the specific study.
However, I think that the third paragraph (lines 81-90) would fit better at some
point earlier, since it seems to be explaining more what was generally said at the
beginning about climatic changes and their importance, and not so much after the
aim of the study mentioned in the previous paragraph (lines 71-80).
•
At the final part of the introduction, it seems that some general information about
the site is mentioned, as for example temperature and also the various reasons that
the specific site was selected. Perhaps, this info could fit better at the “Study Site”
section.
•
As a reader, I would like to see a map showing the location of Camels Hump as
well as the various locations where data were collected. Also, although in lines
146-155 you define the kind of forest types that occupy the area I was a bit
confused on what type of understory species existed at the specific locations that
measurements were taken. Maybe a kind of map showing those locations could
also help in this matter.
•
The numbering of the different sections was not very clear. For example was the
“Study Site” included in the introduction or was it a different part? Both have the
letter A.
•
The text contains a lot of jargon which makes it difficult to understand for a nonexpert in this domain. For example what is the nested plot design (line 167), the
vegetations survey plots (line 156), the dbh (line 178), the boreal/deciduous
ecotone (line 284) etc. Could there be a small section or perhaps a table
explaining basic terms?
•
At page 10, lines 238-245, perhaps you could explain a bit more some terms
except the parameter estimates.
•
The conclusions seemed to be missing some points mentioned earlier in the
discussion. For example, the importance of the overstory to the understory’s shift
as well as the anthropogenic disturbances that may have affected the movement of
the species.
•
In figure 2, I think that some use of arrows like the ones used in figure 3 could be
very helpful. Also, although the figure captions are explained in another page
some kind of legend on the plots could help visually the reader. For example you
could add the years on figure 2 or what the axis mean in figure 4 and 5. Also, the
letter notation is missing from figure 4.
Generally, as I mentioned previously it is obvious that there is a lot of work behind
this paper and in my opinion some clarifications and adjustments could make this paper
easier to read and would be very helpful for the readers.
Review of
Using Long-term Ecological Data to Identify Altitudinal Shifts of Species and
Communities in Response to Recent Climate Change
This paper looks at how vegetation has changed on Camel’s Hump since 1964.
Two main hypotheses are laid out; one saying that as climate changes each plant type will
react differently to the changes, the other saying that communities of plants will all move
together during changes. These hypotheses were tested by laying out plots on the
mountain and checking what types of plants were in each of the plots over time. After
full analysis, it is obvious that there has been a large shift in the plant populations since
1964. In addition, it is clear that the plant types are moving up the mountain individually
instead of communities moving together.
This was a very good paper and for the most part easy to read for someone who
knows very little about the subject. The data seems to be very good; the only thing that
bothers me is that the plots had to be moved after 1964 because of destructive sampling.
Your interpretations make sense given what you observed and really are what I expected
from the beginning when reading the paper. The writing for the most part is very clear
but sometimes it was hard for me to follow simply because I do not have the necessary
background in this field. The graphics seem to be fine but again are difficult for me to
interpret given that I have little background in this field.
I believe the paper should be accepted with minor revisions. I think this paper
presents very important information for the world at large so that we can better
understand how vegetation will change as climate continues to change. The revisions
below, except for #1 and 2, are based on my on ignorance and ideas for expanding the
paper to a wider audience.
1. I believe you should fully explain why you could still use the data from 1964
given the destructive sampling. Some might think it would be best to start with
the 1979 data.
2. I think you need to add a figure with a map showing where the sampling site is.
3. I would like to see a better explanation of what NMDS is.
4. I think a reduction for abbreviations could help the paper to be easier to read.
5. I think better explanations of the figures could help specifically completely
describe what each axis is and what it means.
From what I can tell this paper follows the requirements, my only concern would
be the style of the abstract not fitting what I normally see and having subsections.
Charles Trodick
Eric Portenga
Writing Seminar
February 4, 2009
Pucko and Beckage Review
This study is a continuation of the long-range observations of ecological variations in
plant diversity on Camels Hump in the Green Mountains. It focuses on two competing
hypotheses of species migration as a result of warming climates and whether species shift
geographic locations individually or as a community. Plant communities are observed to be
dissolving as individual species shift in elevation, both up and down the mountain, resulting in
new species communities hitherto unseen in this area.
I think the data presented in this paper and interpretations taken from physical and
statistical observations provide strong support of the authors’ conclusions. Though I am not
familiar with the analyses used, I was able to understand the authors’ intentions by means of the
visuals provided in the figures with time.
This paper furthers the observations of the floral diversity of Camels Hump and
challenges hypotheses of how these communities are changing through time with respect to
changes in climate through time. Since the same site has been carefully studied for over 40 years,
I would deem this paper publishable with some revisions:
•
Introductory phrases such as “However,” “In other words,” “In as much as,” and
“If...” are overused and detract from the strength and forwardness of the ideas
being presented.
•
Some sentences include a lot of different ideas that might be easier to follow if
split into simpler phrases.
I thought the synthesis of the Results and Discussion sections worked to the authors’
benefit because so many observations were taken and analyzed, it was easier to follow with the
interpretations accompanying the observations. I think there would be a lot of flipping back and
forth between the two sections if they were split. The flow from observation to interpretation is
smooth and the transitions between different observation-interpretation sets are well set-up.
Paper Title: Using long-term ecological data to identify altitudinal shifts of species
and communities in response to recent climate change
Paper Authors: C. Pucko and B. Beckage
Reviewer: Lance E. Besaw
Date: 2/4/09
Summary
The authors investigate the temporal and spatial changes in understory communities as a
response to climate change and acid deposition. They use vegetation survey data gathered
from 1964-2006 from Camels Hump, VT to look at overstory and understory community
changes (both direction and magnitude). They found climate change and acid deposition
impacts to be major drivers of species composition change at their study site. They found
that species are shifting independently in elevation direction and magnitude which
suggests they are not moving as units.
Evaluation
The data collection seems very sound. The presence of permanent plots is very important
in this study as it reduces the possibility of data non-stationarity. Also important is the
utilization of non-destructive sampling techniques.
As someone unfamiliar with the field of study, I found the Methods sections to be
difficult to follow conceptually. Many of the paragraphs do not clearly state their
purpose, especially sections “Species data” and “NMDS”. The authors’ interpretation
and explanations of their findings seem defensible. I have no background or experience
that allows me to contend with any of their arguments. Overall, the figures do a good job
relaying the authors’ findings and interpretations to the reader. Captions are informative
and provide adequate description of the displayed concepts.
Recommendation
Overall, I think the manuscript’s contribution is significant. I recommend the manuscript
be accepted with minor revisions; those being corrections to increase the read- and
understandability of the paper. The manuscript provides great insight to the ecological
migration of over- and understory species.
Specific Comments
The introduction does a good job of reviewing the literature and framing the importance
of the paper’s contribution.
Several run-on sentences exist in the document and should be separated to increase readand understandability.
Many paragraphs do not start with “topic sentences” which make the paper difficult to
read. I would suggest restructure many of the paragraphs and starting them with topic
sentences to highlight the important information contained within them.
1
Luke Reusser
GEOL 371
Feb 4th, 2009
Review of:
Pucko, C., and Beckage, B., Using long-term ecological data to identify altitudinal
shifts of species and communities in response to recent climate change.
Planned submission to:
Diversity and Distributions.
In this manuscript, the authors report their findings from a long-term ecological
study of plant and tree community and species shifts from 1965 to 2006 in the montane
environment within Camels Hump State Park. The over-arching aims of the study are to
determine 1) how plant species and communities shift in elevation in response to
anthropogenic climate change, and 2) whether individual species within communities
respond similarly, or individualistically to changing climate over the period of study.
With the aid of non-metric multidimensional scaling (NMDS) and Bayesian models, the
researches determined that 1) between 1965 and 2006, understory communities have
become more homogenous and low elevation communities have shifted to higher
elevations, 2) while some species have shifted upslope, others have remained relatively
stationary, and several have actually shifted downslope, and, 3) the average elevational
shift of understory species is almost double that of canopy species indicating that
understory species shifts can not be attributed solely to soil chemistry and light
availability determined by canopy conditions. Their findings suggest that plant
communities are currently undergoing a reshuffling of species in response to warming
climate that may have implications for competitive interactions and ecosystem function.
Further, their study demonstrates the importance of incorporating individual species
analysis into models of large-scale community dynamics in order to maintain biological
accuracy.
Overall, this manuscript is well written and clearly organized. Understanding
how plant communities have and will continue to respond to climate change is imperative
in today’s world, and this study offers intriguing findings for northern mountainous
regions. This manuscript should definitely be published with revisions, and perhaps
some reorganization.
Below, I have listed key suggestions by section. Refer to the actual manuscript
for smaller more detailed corrections and suggestions.
Abstract:
Will the abstract be restructured into paragraph form, or will it remain in outline form as
it stands right now. I looked through the guides to authors thinking that this form was
required by the journal, but couldn’t find any abstract specific instructions.
Introductions:
1. The intro lays out well the importance of this study and your specific
hypotheses. However, at present it seems somewhat long. I would suggest
2.
3.
4.
5.
narrowing in on the big ideas you are going after and stripping out some of the
other stuff. Refer to the manuscript for detailed comments.
An interesting notion you bring up in your conclusions is that large-scale
models today take a community approach, and in doing so, they may not be
completely biologically accurate. This is a really important finding, and I
think it is worth stating it more directly in the intro. Maybe somewhere in the
later part of the first paragraph.
This probably isn’t really important, but it kept popping up for me. When you
discuss the two dominant ways researchers think about community vs. species
shifts, you refer to them as “hypotheses.” I read them more as theories, but
maybe this is semantics.
The first sentence of the last paragraph on page three is really long. I had to
read it several times to pull out what you were getting at. May be better to
split it up, or lead with the ending clause “It is increasingly important…” so
folks know right up from what you are trying to get across.
The second paragraph on pg 4 (starts at ln 103) doesn’t seem to logically
follow the preceding ones. Maybe consider folding this paragraph and the
next into the study site section.
Study Site:
Reads pretty well as is. Provides all the pertinent details. As a geologist, the first thing I
want to see in a paper about a specific place is a location map. And perhaps even a
picture showing typical flora in a montane environment.
Methods:
1. (Field) Again, being a visual person, I wanted to see some sort of schematic
figure depicting the plot layout you describe in this section. Maybe have plot
boxes overlying a topo map of camels hump.
2. (Species) Just want to make sure I understand this. For each of the quadrants
with six understory sub-plot, you did a separate survey in each sub-plot, and then
averaged the result to get one percent cover for the whole quadrant right? Also,
how variable were these estimates? Did you propagate these errors through
further analysis?
3. (Statistical) For the NMDS, on page 9 you state that the technique shifts point the
cluster more similar points. Does this artificially increase the difference between
things? Just seems a little fishy to me, but I really don’t have much multivariate
statistical background. Did you try doing a PCA? Why did you choose the
NMDS over PCA?
4. (Statistical) Exactly what information was included in the NMDS analysis?
5. (Statistical) On line 229 on pg 9, you state that estimates were based on average
basal area per plot. Is this based on you dbh measurements?
6. (Statistical) Line 254 page 10….what is a “mast” year?
Result and Discussion:
I like how you have written these as one section separated by major findings instead of
results vs. discussion. I think it works well given the information you are trying to
convey.
1. (Community) The wording in the first paragraph of this section is a little difficult
to follow. Particularly lines 266 and 267. What I get from the looking at figure 2
is that 1) communities are much more homogenous today than in the past, and 2)
communities at higher elevations today look more similar to those at lower
elevations, i.e. communities are shifting upslope. I think it is just an issue of
sentence structure, unless I am totally misunderstanding something.
2. (Community) I know in PCA, each Principal Component is a combination of
several variables that are usually listed. Is it the same for NMDS? Can you list
the variable that each axis is composed of?
3. (Community) I found myself wondering a lot about error while looking at figure
2. How is error handled in NMDS? Also, how did you account for whatever
errors were associated with the averaged quadrant sub-plot data?
4. (Community) On page 13, lines 301 and 302…you have an empty reference. I
definitely think some citations would strengthen this claim.
5. (Species) I had another question about error here. Figure 4 is missing axes
labels, so I’m note exactly sure what I am looking at, but my wonderment is
whether or not these shifts are significant. Is there anyway to denote the amount
of error in this analysis?
6. (Species) I found the finding that understory shifts were twice as fast as overstory
to be really interesting. I think you could even go into a little more detail about
this in the discussion. One question I had pertains to the table…it seems like
there was a reverse in the overall amount of shift between 1965 and 2006, yet
there is no mention of this in the text. It got me wondering what your thoughts
are on this.
Conclusions:
1. Can you provide any specific examples of competitive interactions with regard to
the species you encountered on camels hump? Are there species that occupy
similar ecological niches that are now shifting into places where they will
compete?
2. I think the last sentence of your conclusions is very powerful, and as I stated
earlier, I think you should draw attention to this in the introduction. Your
findings suggest that it probably isn’t that kosher to ignore individual species
dynamics when modeling large-scale vegetation communities.
3. How applicable do you think your findings are to other montane environments?
Figures and Tables:
I think including a location map would be very beneficial considering that this
paper is site specific.
In addition, again because I am a visual sort of guy, a simple picture of typical
green mountain forest and understory could help in setting the context. Could be a subpanel in a location map figure.
Figure 1: You could perhaps include the regression models in these figures, and
maybe overlay the temp increase for both Burlington and Mansfield.
Figure 2: I like this figure a lot. Clean, easy to understand. The only thing I
would suggest would be to include the component variables of each axis in the caption.
Figure 3: Another nice figure. Can you remove the text overlying most of the
plots? If it is important, define it in the caption.
Figure 4: This one is a little confusion. Above all, you should include axes
labels. I assume Y is frequency percent, but I can’t tell what X is. At first I thought it
was elevations, but seeing as camels hump summit is 1244 m, this can’t be so. Is it
elevation in feet? If so, need to make it meters and label. Also, there is the issue of error
here. Which of these shifts are actually statistically significant and which are noise?
Figure 5 and 6: These also need x-axis labels. You state meters in the captions,
but good to include on the plots themselves too.
Table 1: For the understories, why does the trend reverse between 1986 and
2006? Also, do you have data for more overstory time steps?
Nice paper! Good luck with edits and getting it out the door.
Luke
Meredith Clayton
4 February, 2009
Review #4: Using Long-Term Ecological Data to Identify Altitudinal Shifts of Species
and Communities in Response to Recent Climate Change
This article presents the results of over 40 years of ecological data collection on
Camels Hump, located in the Green Mountains of Vermont. More specifically, the
purpose of the study presented in the article was to determine whether montane
understory plant communities have shifted as intact units, or whether species are
responding individually to documented changes in climate over the study period (19642006). Data was collected through repeated vegetation surveys completed during this
period and were analyzed through non-metric multidimensional scaling (NMDS) and
simple Bayesian models. The results of the study illustrate an overall increase in
homogenization of species composition with varying amounts of change in composition
across elevations. The greatest amount of change is occurring in the highest elevations
and lower elevations are exhibiting the least amount of change. Bayesian models indicate
shifts in the optimal elevations of individual species in terms of magnitude and direction
through a wide range of migration patterns. While some species appear to be moving
upslope, others are shifting their optimal elevation downslope. The average increase in
the elevational optimum of understory species was nearly twice that of overstory species
during the same time period, suggesting that shifts in understory vegetation are
independent of overstory elevational shift. Overall, examination of spatial and temporal
trends in understory communities indicate that climate change and acid deposition are
major drivers of change in species composition in the Green Mountains since 1964;
however, study results for individual species suggest that past communities are not
moving as intact units, but are responding to climate change individually.
Overall, I believe that this is a well written paper that presents important
ecological data in a relatively clear manor. I would recommend that this paper is accepted
by the journal following the consideration of a few minor revisions. As a whole, the
clarity of the writing is good; however, revision of a few run-on sentences noted in the
text is recommended. The introduction is rather lengthy but provides a detailed
description of the study site, justification for such a study, and background information
surrounding the development of hypotheses for this study. This section contains valuable
information for a reader, particularly one who might be unfamiliar with the Green
Mountains, but I recommend re-organizing it slightly to remain effective but more
concise. The only other issue pertaining to writing clarity that I noted was with the results
and discussion section under the community shift heading. This section states that there
has been a downward shift of communities but then states a few sentences later that there
is an upward migratory pattern. I may be interpreting this section incorrectly, but as it is
worded currently it appears to be unclear. In addition, I would suggest consideration for
how much reference is made to the impacts of acid deposition on these shifts. The
abstract mentions acid deposition as a major factor; however, there is very little
supporting evidence provided in the article. It may be relevant to note this factor but
without supporting data in the article I believe you should consider eliminating it from
the abstract.
The data appears to be of good quality and the logic of the interpretations is clear. It is
difficult for me to assess the quality of NMDS data in detail, as I have almost no
experience with it. My initial reaction to the data exclusions described in the article was
concern; however, justification for the exclusions seems reasonable. On the other hand,
there was no explanation for the use of average basal area in overstory plots rather than
the use of species frequency as seen in the understory plots. I can assume that this was
used in an attempt to highlight the presence of new/younger trees but clarification of this
choice in the text is recommended. Illustrations provided with this manuscript appear to
clearly demonstrate the results described in the article. The caption to Figure 2 is lacking
a reference to chart b and this should be added prior to submission. In general, this is a
good paper and it is close to being ready for submission. There has obviously been a lot
of effort and hard work put into this piece and it shows.
• Revise introduction to make more concise
• Improve clarity of explanations of community shifts in results and discussion
section
• Revise run-on sentences noted in the PDF
• Provide explanation for exclusion of frequency test for trees and substitution of
average basal area
• Revise caption for Figure 2 to include reference to chart b
• Consider reference to acid rain in abstract. You touch on this very little in the
article. Your focus here seems to be climate related shifts
Review of: Using long‐term ecological data to identify altitudinal shifts of species and communities in response to recent climate change Main author: Carolyn Pucko This paper approaches a complex phenomena, the shift of species and communities, and uses a long‐
term case study to provide conclusions. Data on species composition, collected from plots at different elevations on Camel’s Hump in VT, were analyzed temporally to determine any noticeable shifts in species. This case study is used to answer part of a more global question: are shifts in species occurring individualistically or are they occurring as species communities? Furthermore, are these shifts creating novel communities due to anthropogenic climate affects? Statistical tests were performed on the data to detect changes that occurred to both overstory and understory plant communities from 1964 to 2006. The analysis showed that overall, species were migrating to higher elevations, but the rate of shift was greater at the higher elevations. Another important aspect of the analysis was that individual species were considered to be moving differently from their normal communities. The idea that novel communities are forming raises concern for conservationists, and this idea confirms that individual species should be used for modeling future vegetation. This paper seems like it will be a great asset towards this area of research, and with some minor revisions this paper should be accepted. Describing the changes in multiple parameters over time is not a simple task, and the analysis in this paper deciphers important shifts in species over time. I am not an expert in plant biology but I can see the value of this research because the introduction and conclusion draw evidence that these possibly detrimental changes are due to climate change. The paper was laid out logically, and the literature review in the introduction provides a good perspective on this field of research. The study location is described well; it is established in the intro and then described in detail in the Study Site section. A visual representation of the study site could be a good addition. The NMDS figures in the manuscript are informative, but the most important aspects of these plots might be able to be displayed more simply (is there anyway to put some of this in a table). Maybe you could display one or two representative plots from figures 2 and 3. The general trend from one plot can be described as being similar to the trend in the other plots. Make sure that legends in the figures are separated and brought to the end of the manuscript, per author instructions. Following are some more suggestions I came up with: •
‘we’ is used many time on page 3. You could probably get rid of the ‘we’s altogether, because I do not think there are many other ‘we’s in the paper. If you use ‘we’ at least make sure it is used consistently (eg. Either your group, or the scientific community). •
Page 5 you have a paragraph on statistical methods in the introduction: this last paragraph could be condensed to a sentence because most of the content in that paragraph is mentioned in the Statistical Analysis section. •
In the Field Methods section (page 7) you describe the experimental setup well in words, but a diagram showing what a sampling plot looks like (and maybe where the plots are laid out on Mt. Mansfield) could be beneficial. Having a contour map could help with displaying the elevations you are describing. •
The equations on page 10 could be simplified, because currently there are a lot of components (constants and variables) that are not described in the text. Could you maybe reference a statistical text with this analysis described? Good luck with the editing, Martin Paper: ‘Using Long-term Ecological Data to Identify Altitudinal Shifts of Species and
Communities in Response to Recent Climate Change’ by Carolyn Pucko
Reviewer: Nikos Fytilis – 02/03/09
This paper’s goal is to determine the magnitude and direction of change in understory plant
communities located in Camels Hump in the Green Mountains of Vermont due to the documented
changes in climate over the past 40 years. The authors try to find patterns in order to define
whether species are responding individualistically or as intact units. The statistical methods and
models used in the paper presented (NMDS, Bayesian model) include both overstory and
understory plant communities. The results indicate spatial and temporal trends of change in
species compositions closely related to climate and acid deposition but at the same time the
magnitude and direction of elevational change indicate that species are moving as individuals.
The abstract is well organized. It gives a great overview of the whole paper. Although
you mentioned during the previous class that this is not the final format of your paper – especially
the results/conclusion section, I think that you need to check the numbering of the sections. Also,
I found the introduction too big and I believe is a good idea to split it in half (introduction,
assumptions, related to study site??). One other point I would like to mention is that in page 4
where you give the temperature raise since 1963(last paragraph), if I understood Figure, the range
of the values should be higher. I particularly loved the way you present the data collected and the
related references in this section especially if we consider the amount of the information. The
audience of the journal will follow the logical way you presented your thoughts and assumptions.
In the section where you describe the study cite, I don’t know if it will be helpful to add
more data from other environmental parameters such as moisture, hours of sunshine per day and
others. In the second paragraph where you describe the occupancy of the area, a map of the area
and the major forest types would provide a better overview of the area. The same thing could be
applied in the field methods section. A map made by using appropriate software could show the
nested plots. The use of many acronyms was a problem for me but the readers of this journal will
be experts so it is up to you if you want to add a glossary at the beginning of the paper. Also, in
page 7 you can specify where the remaining 113 species belong to and what method you used to
count the stem. At the next section you could explain more the parameters and variables used in
each model (understory and overstory). Additionally, I would like to ask you how you come up
with the 48 species you mention in the top of page 11. It was very good the part where you point
out the reasons you select NMDS and especially the comparison with the PCA.
Again, as you said in the class you need to re-organize the last section with the results,
the future steps and the discussion. In this part of your paper you use two acronyms which I
couldn’t understand what acronym BDF stands for. Maybe, you can create another table with the
species you are referring to in lines 325-327. As for the figures, could you show bigger the arrows
in Figure 3a, b, c? In Figure 4 I think that you have to put the letters in each Figure since you
mention them in the conclusion even though you explain them perfectly at the end of your paper.
Finally, in Figure 5 and 6 I couldn’t found what y axis stand for.
General, I believe the paper is perfect and the whole project is very interesting. With
some revisions, the paper should be accepted and published. Good luck and congratulations for
your excellent work.
February 4, 2009
J. Nunery response to Pucko and Beckage
Using long-term ecological data to identify altitudinal shifts of species and communities in
response to recent climate change
Climate change may be affecting plant communities in the Green Mountains of Vermont.
Trends in elevational migration were noted in species throughout the study area. However,
despite the over-arching unidirectional trends, a closer look at individual species migration
showed that plant communities are not migrating as intact units. This study showed the
importance of individual species modeling in more accurately projecting species and community
response to climate change.
Results from this paper are a valuable contribution to our understanding of plant response to
climate change at both the individual species and plant community level. This paper will inform
future work attempting to model species range shift, and plant community response to a
changing climate. However, the paper would benefit from several stylistic changes that may
help the overall message be more clearly stated. In general, shorter and more concise sentence
structure would help with the flow of the paper (see comments on pdf). Also, use of the active
voice will help strengthen the paper, and aid the author in clearly stating their point.
The introduction provides a thorough overview of the issue at hand, study site, and basic
methodologies. However, it begins to lose focus towards the end. Around the last paragraph on
page 4, information that is more relevant to the methods section is given in this section. By
separating details of site history and statistical analysis from the introduction section you might
be able to maintain a more clear and concise introduction that frames the issue at hand.
More broadly speaking, the addressing several other factors that may affect understory species
composition would strengthen this paper. In addition to possible explanations of species
compositional changes over the last 40 years given in the paper (acid deposition), a review of
successional and stand developmental dynamics would be helpful. Species composition and
community assemblages change throughout stand development. This should be recognized, and
it should be justified that the results seen in this study are not a result of successional or stand
developmental dynamics.
Specific comments
L51: This citation makes it look like IPCC states that mechanisms of species shift is a
fundamental objective of ecology, in addition to anthropogenic climate change, is this accurate?
L83-84: I am not clear as to exactly what you are talking about here. What components
specifically are you addressing?
L87: geographic or elevational? Are you measuring elevational gradients and using this to make
inferences on geographic range shifts (can you assume that the two are equivalent)?
L110: This phrasing implies that there is a gap of surveys between 1965 and 2006, be specific as
to the exact years your data covers. Are they annual surveys, decadal, etc.?
L114: What is the temporal range associated with this temperature increase, is it 1965-2008?
L154: Is Mountain paper birch Betula cordifolia or Betula papyrifera var. cordifolia
L162: How much is "some". Readers who are familiar with the northeast history of the selective
logging of red spruce will question the use of “some”. The more specific you can be the better.
L164: How close to the outside of the research area did logging occur. Edge effects may
influence understory vegetation, especially if invasive species are an issue, which they probably
are not in this area.
L171: Instead of using “up” what about “on an elevational gradient along”
L178: Spell out greater
L181: What was the size of the PVC frame?
L183: Did you separate shrubs and seedlings? This might be very important, and should be
specifically stated.
L195: Specify that data was aggregated by genus.
First paragraph page 9: Try to use the active voice at least intermittently to avoid excessive use
of the passive voice.
L230: Are these two different things or are you defining optimum elevation? The use of “or”
implies that they are different.
L273: Is the homogenization occurring as a result of the temporal scope of your project. Perhaps
you are seeing the beginning of species movement, and overtime the lower elevation species
composition may alter as latitudinal range expansion catches up with elevational range
expansion.
L277: Do you expect or did you hypothesize; expecting implies a sense of subjectivity in your
research, while hypothesize maintains objectivity.
L282: Can you make inferences about disproportional rates of species migration between
latitudinal and elevational migratory rates.
L310: Was this loss entirely from acid deposition or also from selective logging at mid
elevations?
L337: This would be a good place to link in succession and stand development - as these are two
important factors in understory community changes that should be addressed.
Table 1: What happened between 1983 and 1986 to affect the means so drastically? Why these
year breaks? You should justify why you chose these breaks in the table description.
Mark Isselhardt Critical Writing (Geology 371) 2/4/09 Pucko, C and Beckage, B. 2009 Using Long‐term Ecological Data to Identify Altitudinal Shifts of Species and Communities in Response to Recent Climate Change for submission to the Journal of Conservation Biogeography. The authors examine the impacts of recent climate change on montane forest understory communities and individual species. One particular focus is distinguishing if and how communities have shifted in the 40 years since data was first collected. Another focus is the way in which species are responding; individualistically or as established groups. The results are of broad relevance to predictions of future climate impacts. This paper uses sophisticated data analysis in an attempt to answer these questions. The result of the analysis indicates that the understory communities have changed not as complete units but more individualistically. This paper is written clearly, presents original and compelling results and deserves publication. That being said, the paper could benefit from a few minor changes in grammar (see annotated version for mostly stylistic suggestions) and a few additions to the methods and discussion. The ample introduction supplies background information to support the study’s hypothesis. The introduction also brought up the issue of individual species life history traits. It is suggested that certain species may be more reactive then others to a changing climate. It would be helpful to include some information about the sites understory species diversity. Reporting some measure of diversity would help the reader get a handle on the community’s composition along the elevation gradient being discussed. The interpretation of the results is combined with the discussion in an effective way. Figure 1 is used to illustrate the change in air temperature at two elevations over the last 40 years. I think this data might be more clearly presented as a table with distinct mean temperatures for each site as well as a calculated change in mean temp. The results of NMDS and simple Bayesian models demand careful interpretation. I assume the readership of JCB is familiar with these tools but to unfamiliar eyes, understanding these techniques and the subsequent data is challenging. The methods section could include a generalized illustration that shows common rules to interpreting a NMDS graph and/or the plots of Bayesian models. Figure 4 seems to show a lot of variation in how specific species react to the changing climate. Could there be some discussion of how and why this might be? Could it be connected to species life history traits being more advantageous? The observation of lower elevation plots shifting inversely to the rate of warming was interesting. The potential impacts of acid deposition certainly deserve the attention given in the results section. Is there room for speculation as to how the loss of 50% of the red spruce basal area in the overstory could have still impacted the results? What if there loss hadn’t occurred? •
•
•
•
Figures 2‐6 could use more detailed axis labels. What are the units? Could the X axis on Fig 5, 6 have a narrower scale? The results presented in Table 1 are not discussed in much detail during the body of the paper. Were these values the result of the Bayesian model? There is a high level of precision with these values. Is there any way to estimate the accuracy? Did the understory have shift less from ’65‐’06 then from ’65‐’86? How? How about a picture showing an understory plot being measured? How about a simplified contour map of the study area with the plot locations overlaid? The paper seems to conform to the formatting guidelines presented by the Journal of Conservation Biogeography. Using Long-term Ecological Data to Identify Altitudinal Shifts of Species and
Communities in Response to Recent Climate Change
Carolyn Pucko & Brian Beckage
Review by Andrea Pearce, 4 Feburary 2009
Vegetation research plots have been maintained on Camel’s Hump, Vermont for
approximately 40 years. This research aims to track the migration of understory plant
communities over time as a response to global climate change citing a 1-2 degree C
warming in the vicinity of Camel’s hump. The author tests the hypotheses that the
understory communities either shift up elevation as intact communities or that individual
species shift up and down elevation independently and whether these shifts are linked to
changes in the overstory. Non-metric multidimensional scaling and Bayesian modeling
are two statistical tools used in the analysis. Communities at higher elevation showed
more shifting than communities at lower elevations, despite that the lower elevations
experienced greater warming. Species migration patterns vary in magnitude and
direction indicating that communities are not remaining intact as they shift in response to
global climate change.
The authors make good use of a rich long-term ecological monitoring dataset. Through
the introduction they convincingly argue that distinguishing between the types of species
shifting will be important to future ecological modeling. The authors keep the discussion
and conclusions firmly focused on the data at hand. The only significant area of
improvement from my (humble) perspective would be providing the reader with more of
a basis for the computational analysis. Since the discussion and conclusions focus so
heavily on the results of these analyses, it is worth more time and space in the
introduction and methods sections more explicitly describing the analyses. You do
describe how to interpret the NMDS which is very helpful, but more introductory
references for the reader would help them reproduce this type of analysis on another
dataset.
I recommend this manuscript be accepted with minor revisions. The subject of this
research is appropriate to the journal and timely. Minor editorial comments are included
in the attached annotated text. Additional comments are listed below. The first comment
below is the most important in my opinion.
o The introduction is well written and thoroughly covers the issues related to the
vegetation including a good review of relevant literature. The reader may benefit
from a slightly expanded introduction to the NMDS and Bayesian methods
including citing research using these methods in similar ways.
o You provide a very nice description of the research site, including geology, and
overstory vegetation. Would it be useful (possible?) to also introduce the
understory communities since they are the focus of the research?
o Field Methods section – While you describe creating an inventory of woody
species, you never explicitly mention doing the same for herbaceous species? Are
you? (This may be understood, but this isn’t my field. I may be misinterpreting.)
o Figure 3 – The text on these NMDS plots is confusing and it does not appear in
each sub-plot.
o Figure 4 – Is there any significance to the weight of the red and green lines?
Some appear thicker than others.
Good job and good luck!